Whole Body Growth Objectives Draw growth curves Explain

Whole Body Growth

Objectives �Draw growth curves �Explain different changes in body measurements �Explain different changes is body components �Explain different changes in carcass components �Explain different changes in chemical composition

Video �Foal growth video

Growth Curves �Represents an increase in size relative to a period of time �Often impacted on compositional levels of varying tissues • Muscle, fat, bone �Dependent on plane of nutrition and stage of development �Four phases of growth (figure 9. 5)

Sigmoidal growth curve �What do you notice?

Age vs Maturity � Chronological age • Age in absolute time e. g. days weeks months � Physiological age • Stages of development that may be discerned by specific physical or chemical stages of development or function � Maturity is the point in time when an animal reaches its highest level of complexity or development � Absolute growth rate: utilizes units • ADG, WDA, Birth, Weaning, etc. (Figure 9. 9) • Growth rates of various tissues (figure 9. 11)

Changes in Body Measurements �Quantifiable �There are measurements specific to the livestock industry • Carcass length • Longissimus muscle area • Subcutaneous fat thickness �Carcass length in pork – value • Standard reference points of measurement

Changes in Body Components �Body Weight �Empty Body weight �Dressing Percentage �Carcass Weight

Body Weight �First method used to evaluate an animals ability to produce edible products �Although not always accurate • Rumen has a large amount of fill • Must withhold feed and water for 24 hours prior to slaughter • Secures shrunken weights

Empty Body Weight �Accounts for the digestive system content �Accomplished by flushing digestive tract and weighing empty tissues

Dressing Percentage �Dressing the animal • During slaughter portions of the animal are removed • Internal organs, hide, feet and head �Most important pieces remaining • Muscle, bone, and fat �Dressing percentage is calculated by dividing the carcass weight by the shrunken live weight of the animal

Carcass Weight �Carcass weight as growth end point is highly desirable �Carcass weight is routinely used as a primary end point • Muscle, bone, fat

Changes in carcass components �The composition of the carcass has a major effect on economic value of the animal �Growth of individual carcass components (muscle, bone, and fat) may be plotted against time to better characterize these differences.

Changes in carcass components

Changes in carcass components �Bone- increases at a decreasing rate �Muscle is the fastest growing during early life and post weaning, yet decreases with time �Fat is the fastest growing at physiological maturity �A decrease in bone and muscle is due to the extreme increase in fat percentage

Changes in the Chemical Composition � Chemical Composition changes with time and weight • Because bone, muscle, and fat are deposited at different rates � Muscle ranges from 68 -85% water � Moisture to protein ratio = 4: 1 � CT increases with age � Muscle fibers increase in size, yet CT decreases in percent thus increases in size � Fat • More variable yet accumulates in various depots with age including the depots associated with muscle

Factors affecting Carcass composition �Genetics �Species �Selection and domestication �Muscle distribution �Fat distribution �Breed �Frame size �Sex

Genetics �Mutation or intensive selection �Influence of environment �Phenotype versus genotype �Heritability estimates

Species �Variation between species �Deposition of tissues, especially fat �Order of fat deposition between species �Proportion of composition compared anatomically �Value differences among composition parts of each species

Muscle distribution �Comparison of muscle • distribution between species �Ruminant versus non-ruminant �Domestic versus non-domesticated species �Meat versus milk type selection

Fat distribution �Species is a major determinant in fat deposition �At the beginning, carcass fat is fairly even in distribution �However, a growth increases and maturity develops fat begins to accumulate varying percentages at different anatomical locations

Breed Variations �Various • • breeds have: Different maturity patterns Frame sizes Meat versus dairy type Selection pressure for muscling

Frame Size �Growth patterns �Feedlot gain and efficiency �Chronological vs Physiological maturity �Quality Grade vs fat deposition �Compositional Endpoints �Dairy vs Meat type �Dressing Percentage variations �Forage availability and utilization

Frame size

Frame Size

Sex �Except for pigs, females mature earliest �Intact males have a greater proportion of muscles in the forequarter while heifers in the proximal pelvic limb �Castrated males are intermediate �Heifers at the same physiological slaughter age and maturity will be fatter lower yielding

Objectives �Draw growth curves �Explain different changes in body measurements �Explain different changes is body components �Explain different changes in carcass components �Explain different changes in chemical composition